Pulse reflection type fault location device utilizing a dark-trace tube display

ABSTRACT

A device for the location of faults on power-transmission lines at the instant of a fault, in which transmitted and reflected pulses are registered in synchronism with calibration markers by a dark-trace tube, which fact considerably increases the speed of response of the recorder.

United States Patent Shalyt et a].

1 51 June 20, 1972 PULSE REFLECTION TYPE FAULT LOCATION DEVICE UTILIZINGA DARK-TRACE TUBE DISPLAY Filed: Sept. 16, 1969 Appl. No.: 858,430

U.S. Cl ..324/52 ..G0lr 31/1 1 Field of Search ..324/52 References CitedUNITED STATES PATENTS Leslie et a].

Devot Youdan Spaulding Primary Examiner-Gerard R. StreckerAttorney-Waters, Roditi, Schwartz & Nissen 57 ABSTRACT A device for thelocation of faults on power-transmission lines at the instant of afault, in which transmitted and reflected pulses are registered insynchronism with calibration markers by a dark-trace tube, which factconsiderably increases the speed of response of the recorder.

1 Claim, 5 Drawing Figures PULSE REFLECTION TYPE FAULT LOCATION DEVICEUTILIZING A DARK-TRACE TUBE DISPLAY The present invention relates topulse-type instruments employed in power generation and distribution,and more specifically to devices for overhead line fault location at theinstant of a fault, said device being used to detect and locate bothsustained and transient faults (including those that may have occurred,for example, prior to a successful reclosure of an automatic circuitbreaker in the associated line).

There exist fault locators for power transmission lines, in whichtransmitted and reflected pulses, controlled by a syncpulse unit, areregistered at the instant of a fault in synchronism with calibrationmarkers by a recorder actuated by a trigger unit connected to theprotective relay circuits of the power transmission line being served.

In existing fault locators, the recorder is a cathode-ray tube completewith control components, and a photographic camera to take photographsof the pulse characteristic of a faulty line from the CRT screen. Suchfault locators display data relative to the position of faults on a linewith a considerable delay being required to develop the film.

One object of the present invention is to provide a device for thelocation of faults in power transmission lines at the instants ofoccurence thereof, which device displays the results with a minimum ofdelay.

Another object of the present invention is to provide a device for thelocation of faults in power transmission lines at the instants ofoccurence thereof, which device excludes mechanical elements from therecorder.

Still another object of the invention is to provide a device for thelocation of faults in power transmission lines at the instant ofoccurrence thereof, which device provides a direct indication of thedistance to the fault.

With these and other objects in view, in the fault locator disclosedherein, transmitted and reflected pulses, controlled by a sync-pulseunit, are registered at the instant of a fault in synchronism withcalibration markers by a recorder actuated by a trigger unit connectedto the protective relay circuits of the line. According to theinvention, the recorder comprises a dark-trace tube whose modulatoraccepts the output of the unit controlling the trace-duration oftransmitted and reflected pulses, actuated by the trigger unit andconnected to the sync-pulse unit.

Due to this arrangement, a fault locator according to the inventionpresents the findings with a minimum of delay.

Other objects and advantages of the present invention will be seen fromthe following description of a preferred embodiment as illustrated inthe accompanying drawings wherein:

FIG. 1 is a block-diagram of a fault locator according to the invention;

FIG. 2 is a block-diagram of the unit controlling the traceduration oftransmitted and reflected pulses of the fault locator of FIG. 1;

FIG. 3 shows the voltage waveforms obtained by means of the faultlocator of the present invention;

FIG. 4 is a time plot of the pulse waveforms generated by the unitcontrolling the trace-duration of transmitted and reflected pulses ofthe fault locator of the present invention;

FIG. 5 is an example of the pulse characteristic of a power transmissionline, obtained on the screen of the dark-trace tube of the fault locatorof the present invention.

In FIG. I, is a fault locator comprising, according to the invention, atrigger unit 1; a unit 2 to control the trace-duration of transmittedand reflected pulses; a recorder which is a darktrace tube 3; async-pulse unit 4; a transmitted-pulse generator unit 5; an amplifier 6;a time-base unit 7; and a calibrationmarker unit 8.

The modulator of the dark-trace tube 3 is connected to the output of thetrace-duration control unit 2, the horizontal deflection coil isconnected to the time-base unit 7, and the vertical deflection coil isconnected to the amplifier 6 and the calibration-marker unit 8.

The pulse from the trace-duration control unit 2 controls the sync-pulseunit 4 which actuates the transmitted-pulse generator unit 5 and thetime-base unit 7.

The trigger unit 1, whose input is connected to the protective relayunit of the power transmission line being serviced, forms at its outputa short-time voltage pulse the moment the protective relay unitoperates.

The unit 2 for control over the record-duration of transmitted andreflected pulses is connected with its input to the output of thetrigger unit 1. Generated at the output of the unit 2 with a preset timedelay relative to the input pulse is a positive rectangular pulse ofcertain duration.

The sync-pulse unit 4 is connected to the output of the unit 2.Generated at three outputs of the former unit in the course of durationof the rectangular pulse are a series of short-time sync pulsesfollowing each other at uniform intervals.

The input of the transmitted-pulse generator unit 5 is connected to theoutput of the unit 4, while its output is connected to the powertransmission line being serviced. The unit 5 generates, synchronouslywith each pulse from the syncpulse unit 4, probing pulses transmitted tothe power line.

The amplifier 6, connected with its input to the power transmissionline, generates at its output amplified pulses transmitted to the lineand reflected from the fault.

The calibration-marker unit 8, connected with its input to the output ofthe sync-pulse unit 4, generates at its output a set of calibrationmarkers synchronously with each pulse generated by the sync-pulse unit.

The time-base unit 7, connected with its input to the unit 4, generatesat its output a saw-tooth wave synchronously with each pulse generatedby the sync-pulse unit. I

The dark-trace tube 3 with horizontal and vertical deflection coilsprovides for recording and displaying on the screen as a dark image thetransmitted and reflected pulses along with the calibration markers fora subsequent determination of the distance to the fault. Connected tothe modulator of the dark-trace tube 3 is the output of therecord-duration control unit 2, the vertical deflection coil beingconnected to the outputs of the amplifier 6 and of thecalibration-marker unit 8. The horizontal deflection coil is connectedto the output of the time-base unit 7.

The trace-duration control unit 2 contains multivibrators 9 and 10 (FIG.2) and resistors 11 through 13 and generates the brightening pulse forthe dark-trace tube 3 and gate pulses for the sync-pulse unit 4.

Basically, operation of the fault locator disclosed herein consists ofmeasuring the time interval between the instant of transmission of apulse into the line being tested and the instant of arrival of a pulsereflected from the fault. This time interval, At, is proportional to thedistance, I, to the fault:

t= 2l/u, so that l= (t/2) u, where u is the velocity of pulsepropagation in overhead power transmission lines.

For better insight into the operation of the fault locator disclosedherein, reference is next made to the voltage waveforms of FIG. 3, wheretime t is the scale of the abscissa and the voltage v is the scale ofthe ordinate. The letters a, b, c, d, e and f designate the voltage waveforms corresponding to the points a, b, c, d, e and f in theblock-diagram of FIG. 1.

In the case of a fault on the line served by the fault locator, closureof the contacts in protective relays (arrow A in FIG. 1) actuates thetrigger circuit 1 (waveform a), which triggers the trace-durationcontrol unit 2 generating a positive rectangular pulse of duration T(waveform b) which goes both to the modulator of the dark-trace tube 3and to the sync-pulse unit 4.

The output pulse of the trace-duration control unit 2 should be delayedwith respect to the instant at which the fault locator is started by atime T, which is the time required for the transients in theelectromagnetic beam deflection system of the dark-trace tube 3 to diedown. This pulse appears across the resistor 13 due to the addition ofpulses of opposite polarities and of durations T and T,, taken from theoutputs of the multivibrators 9 and 10, respectively, through theresistors 11 and 12. Referring to the time plot of pulses generated bythe trace-duration control unit 2 in FIG. 4 (where the time t is thescale of the abscissa and the voltage v is the scale of the ordinate),at I is the trigger pulse; at m is the pulse generated by themultivibrator 9, of duration T equal to the time T of the transients inthe electromagnetic beam deflection system of the dark-trace tube; at nis the pulse generated by the multivibrator 10, of duration T,; and at pis the brightening pulse for the dark-trace tube 3 and the gate pulsefor the sync-pulse unit 4, of duration T T, T,.

The sync-pulse unit 4 operates for a time 1,, as shown in FIG. 3,delivering in the meantime n sync-pulses (the waveform c in FIG. 3)which go to the transmitted-pulse generator unit 5 (waveform d), thetime-base unit 7 (waveform e), and the calibration-marker unit 8(waveform The pulses, both transmitted into the line and reflected fromthe fault, are fed through the amplifier 6 along with the calibrationmarkers furnished by the unit 8 to the vertical deflection coil of thedark-trace tube 3.

The beam writes out the same trace n times, so that the transmitted andreflected pulses are displayed on the screen of the dark-trace tube 3along with the calibration markers in the form of a dark trace, as shownin FIG. 5, where g is the transmitted pulse, in is the reflected pulse,and R are the calibration markers (spaced 10 km. apart).

The operator can determine the distance to the fault directly from thescreen of the dark-trace tube 3' by counting the number of intervalsbetween the calibration markers (both whole ones and the fraction of thelast interval) separating the transmitted and the reflected pulses. Inthe example of FIG. 5, the reflected pulse is located at a distance of34 km.

The display of the pulses and calibration markers persists for a longtime. It can be erased, if necessary, by heating the substrate filmcoated by scotopic phosphor. This is done by passing a current throughthe film.

The fault locator disclosed herein is simple and inexpensive to make,convenient to use, displays data with a minimum delay and can be used onall present-day power-transmission lines.

Although the present invention has been disclosed in connection with apreferred embodiment, it is not to be limited to the details shown, asthere may be modifications and adaptations without any departure fromthe idea and scope of the invention, which those skilled in the art willreadily comprehend.

Such modifications and adaptations should be considered to be within therange of equivalence of the present invention as set forth in theaccompanying claims.

What is claimed is:

l. A device for the location of faults at the instant of occurrencethereof in a power transmission line provided with protective relays,said device comprising: a trigger unit including an input connected tosaid protective relays, said trigger unit including an output and beingadapted to generate at said output, upon operation of said protectiverelays, a short duration voltage pulse; a record-duration control unitadapted for controlling record duration of probing pulses and pulsesreflected from a fault, said further unit including an input connectedto the output of said trigger unit and including and being adapted togenerate at an output with a preset time delay a positive rectangularpulse of predetermined duration; a sync-pulse unit connected to theoutput of said record-duration control unit and including and beingadapted to generate at a plurality of outputs, during presence at theinput thereof of said positive rectangular pulse, a series of shortsynchronizing pulses following each other at uniform intervals; atransmitted-pulse generator unit including an input connected to one ofthe outputs of said sync-pulse unit and including an output connected tosaid power transmission line, said transmitted-pulse enerator uni beingadapted to generate synchronously wl each pulse generated by saidsync-pulse unit a probing pulse transmitted to said power transmissionline; an amplifier including an input connected to said powertransmission line and including and being adapted to generate at anoutput amplified probing and reflected pulses; a calibration-marker unitincluding an input connected to one of the outputs of said sync-pulseunit and including and adapted to generate at an outputa set ofcalibration markers synchronously with each pulse generated by saidsync-pulse unit; a time-base unit including an input connected to saidsync-pulse unit and including and adapted to generate at an output asaw-tooth wave synchronously with each pulse generated by saidsync-pulse unit; a dark-trace tube including vertical and horizontaldeflection coils and a modulator connected to the output of saidrecord-duration control unit; said vertical deflection coil beingconnected to the output of said amplifier and to the output of saidcalibration-marker unit; said horizontal deflection coil being connectedto the output of said time-base unit; said dark-trace tube including andbeing adapted to provide for recording and displaying on a screen, as adark image, said probing and reflected pulses along with the calibrationmarkers whereby provision is made for a subsequent determination of thedistance to the fault in said power transmission line.

i i i i

1. A device for the location of faults at the instant of occurrencethereof in a power transmission line provided with protective relays,said device comprising: a trigger unit including an input connected tosaid protective relays, said trigger unit including an output and beingadapted to generate at said output, upon operation of said protectiverelays, a short duration voltage pulse; a record-duration control unitadapted for controlling record duration of probing pulses and pulsesreflected from a fault, said further unit including an input connectedto the output of said trigger unit and including and being adapted togenerate at an output with a preset time delay a positive rectangularpulse of predetermined duration; a syncpulse unit connected to theoutput of said record-duration control unit and including and beingadapted to generate at a plurality of outputs, during presence at theinput thereof of said positive rectangular pulse, a series of shortsynchronizing pulses following each other at uniform intervals; atransmittedpulse generator unit including an input connected to one ofthe outputs of said sync-pulse unit and including an output connected tosaid power transmission line, said transmitted-pulse generator unitbeing adapted to generate synchronously with each pulse generated bysaid sync-pulse unit a probing pulse transmitted to said powertransmission line; an amplifier including an input connected to saidpower transmission line and including and being adapted to generate atan output amplified probing and reflected pulses; a calibration-markerunit including an input connected to one of the outputs of saidsync-pulse unit and including and adapted to generate at an output a setof calibration markers synchronously with each pulse generated by saidsync-pulse unit; a time-base unit including an input connected to saidsync-pulse unit and including and adapted to generate at an output asawtooth wave synchronously with each pulse generated by said syncpulseunit; a dark-trace tube including vertical and horizontal deflectioncoils and a modulator connected to the output of said record-durationcontrol unit; said vertical deflection coil being connected to theoutput of said amplifier and to the output of said calibration-markerunit; said horizontal deflection coil being connected to the output ofsaid time-base unit; said darktrace tube including and being adapted toprovide for recording and displaying on a screen, as a dark image, saidprobing and reflected pulses along with the calibration markers wherebyprovision is made for a subsequent determination of the distance to thefault in said power transmission line.